Dietary calcium inadequacy may be a contributing cause to osteoporosis, at least for some populations. For example, a positive correlation between calcium intake and bone mass has been found across many age groups. It has also been suggested that the level of calcium intake early in life directly influences the peak bone mass achieved at skeletal maturity.
During the period of late teenage to young adulthood, it has been found that a significant reduction in dietary calcium intake typically occurs. This is especially true of the female population where reduced dietary calcium intake usually happens much earlier in life compared to their male counterparts. Accordingly, females, as a class, are especially susceptible to a prolonged calcium deficit over their life span. This calcium deficit may be one reason for the greater incidence of osteoporosis in post menopausal women.
Calcium can be obtained from a variety of dietary sources. The primary sources of calcium are dairy products, in particular, milk. Milk provides a very valuable source of dietary calcium. However, beginning in late teenage to young adulthood and continuing through later life, milk is typically not consumed in sufficient quantities by the general population to obtain needed levels of calcium. This may be caused by the unattractiveness of milk as a drink for "social occasions". Indeed, it has been found that teenage girls, and especially young adult women, generally find milk to be a socially unattractive drink, as well as too caloric and unappealing in taste. Also, a significant portion of the population becomes lactose intolerant as they reach maturity, resulting in gastrointestinal problems if they consume milk.
To achieve greater consumption of calcium, a more appealing alternative to milk is apparently needed. This alternative must be one which is consumed in sufficient quantities to provide nutritionally beneficial amounts of calcium. Fruit juice beverages are consumed often by the general public at breakfast, especially orange juice. Like milk, orange juice has a wholesome, nutritional image. Also, orange juice is generally considered to have an appealing taste. Accordingly, orange juice nutritionally supplemented with calcium could be viewed as an additional vehicle for achieving greater dietary calcium intake throughout life.
Nutritional supplementation of orange juice, or other fruit juices, with significant levels of calcium is not straight forward. Milk contains, on average, about 0.12% calcium by weight. Inclusion of such a high level of calcium in orange juice requires consideration of a number of issues.
One potential issue is insuring that the calcium, once solubilized, does not precipitate out of the juice. Precipitation of calcium from juice concentrates can be a very significant problem because of the high level of calcium and low water levels present. However, precipitation of calcium from ready-to-serve single-strength juice products can also occur due to the acid systems and other components present in the juice. Orange juice naturally contains a mixture of citric acid and malic acid. The most thermodynamically stable calcium citrate species which forms when a calcium source is added directly to orange juice are also the most insoluble. These insoluble calcium titrate species can precipitate out of the orange juice fairly rapidly.
Ready-to-serve calcium-supplemented chilled juice product have been prepared previously by various methods. One of these methods is referred to as the "premix" method. See U.S. Pat. No. 4,919,963 (Heckert), issued Apr. 24, 1990 and U.S. Pat. No. 4,722,847 (Heckert), issued Feb. 2, 1988. In this method, a meta-stable aqueous premix solution of solubilized calcium is formed with a mixture of citric and malic acid which is then added to reconstituted fruit juice made from a concentrate. The meta-stable aqueous premix solution uses calcium carbonate, calcium oxide, or calcium hydroxide as the calcium source. This solubilized calcium is then added to the fruit juice, plus other fruit juice materials such as fruit juice aroma and flavor volatiles, peel oil, and pulp (or pomace) to provide a ready-to-serve drinkable chilled juice product.
Even using the "premix" method taught in the Heckert patents, ready-to-serve, calcium-supplemented chilled juice products present special calcium precipitation problems. To prolong stability against microbial and mold growth, chilled juice products are pasteurized or sterilized prior to being packed. This typically involves passage of the juice stream through high temperature (typically from about 180.degree. F. (82.2.degree. C.)) to about 212.degree. F. (100.degree. C.)) or ultra-high temperature (typically from about 212.degree. F. (100.degree. C.) to about 260.degree. F. (126.7.degree. C.)) pasteurization or sterilization equipment. Examples of such equipment are plate and frame heat exchangers (high temperature) and direct steam infusion sterilizers (ultra-high temperature).
As calcium-containing fruit juice streams pass through high temperature pasteurization or sterilization equipment, calcium salts present in the juice stream can precipitate out. This is particularly true of calcium-containing citrus juice streams involving calcium hydroxide or calcium carbonate. When these juice streams pass through high temperature pasteurization or sterilization equipment, insoluble calcium titrate can precipitate out which can then deposit on the internal surface of the pasteurizer or sterilizer. Without periodic shutdown and cleaning of the equipment, this precipitated calcium titrate eventually flakes off into the finished chilled juice product stream. In the case of plate and frame heat exchangers, the precipitated and deposited calcium titrate can reduce heat transfer efficiency.
To solve the calcium precipitation problem caused by passage of fruit juice streams through high temperature pasteurization or sterilization equipment, a method called "post-addition" was developed for preparing these ready-to-serve chilled products. See U.S. Pat. No. 5,225,221 to Camden et al. issued Jul. 6, 1993. In this "post-addition" method, an aqueous slurry typically containing about 10% calcium hydroxide is prepared. This calcium hydroxide slurry is then homogeneously dispersed in the pasteurized or sterilized juice stream to provide a calcium-supplemented ready-to-serve, chilled product.
Both the "premix" and "post-addition" methods require the use of water in order to add the calcium source to the juice stream. In order to meet the standard of identity, Not-from-concentrate (NFC) juice products, and in particular NFC orange juice products, can not contain added water. The juice strength, as it is extracted from the fruit, must be maintained. However, the direct addition of calcium sources, in particular calcium hydroxide, to NFC juice streams can cause a number of problems. These include degradation of the juice, and incomplete or inadequate solubilization of the calcium such that solid particles of the calcium source (e.g., calcium hydroxide) or calcium titrate wind up on the bottom of the blend tank. Since NFC orange juice products are desired by a number of orange juice consumers, it would be desirable to be able to develop a process for supplementing such products with calcium that avoids degradation of the juice and incomplete/inadequate solubilization of the calcium, without adding water.